The black stuff coming out of its mouth isn't necessarily a death sentence, it could be just normal post-digestive spoo, or it could be expelling zooxanthellae (sp?), which is a sign of "unhappiness" but again not necessarily the end. Looking deflated is not a positive thing, but even that is something they can bounce back from after a short while. On the other hand, it may be on a decline like so many anemones do shortly after being introduced - this is why you hear so often that they are touchy etc. etc.
I would consider this a warning to review your lighting and other parameters, and make sure they are suitable to maintain an anemone. If they are, it could be that it will bounce back or maybe you got a bad one and it was doomed before you even introduced it.